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Monday, October 25, 2010

I must post this in the midst of my elation before I run into another crippling error

I was composing an email to the R mailing list to ask for help on the issues I described below. Wanting to seem very serious and well-researched, I double checked everything I was doing before sending it. In the process, I found the error. Maybe I should take that as an approach to problem solving in general: write out my problems as if I'm addressing the ultimate experts on the issue. That way if I fail to figure it out, I have a nice message ready to send, but if I figure it out, then I figure it out!

Here's the email:

I'm trying to set up a large cluster of computers at my university
lab. All clients are running XP SP3, and I'm working from a OS X
10.6.4 machine set up as the master; using R 2.11.1 on all machines.

I've succeeded at getting password-less SSH access to the client
machines using Cygwin, but I'm having issues with initializing sleighs
that seem to stem from the "DOS vs UNIX" path-style issues.
I've tried what seem to be two different correct approches, and get
two different errors.

1. The unix-style way; accessing the contents of the C drive through
/cygdrive/c/...:

s=sleigh(
nodeList=c("
lab211-18.mydomain.edu"),
launch=sshcmd,
user="authorizedUser",
scriptExec=envcmd,
scriptDir="'/cygwin/c/Program Files/R/R-2.11.1/library/nws/bin/'",
scriptName="RNWSSleighWorker.py",
verbose=TRUE)

2. The DOS-style way, where the changes are to the "scriptExec" and
"scriptDir" options:

s=sleigh(
nodeList=c("
lab211-18.mydomain.edu"),
launch=sshcmd,
user="authorizedUser",
scriptExec=scriptcmd,
scriptDir="'c:\\Program Files\\R\\R-2.11.1\\library\\nws\\bin\\'",
scriptName="RNWSSleighWorker.py",
verbose=TRUE)

I've verified that the "RNWSSleighWorker.py" exists in the path
"C:\Program Files\R\R-2.11.1\library\nws\bin\" on the client
machine...

At this point I was going to paste in the exact errors I was seeing
and I realized I was missing a directory ("\R\") from all the path's
above, and that I was doing the unix style one with "cygwin" instead
of "cygdrive". Now, the "dos-style way" seems to be working completely
and totally.

So now I can supposedly do parallel computation. I'm almost afraid to take the next step, for fear of what horrors inevitably await!

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